<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button id="myBtn">点击按钮</button>
    <script>
        var myBtn = document.getElementById("myBtn");
        console.dir(myBtn);
        myBtn.onclick = function(){
            alert("按钮被点击了！");
            }
    </script>
    
</body>
</html>